The invention concerns a grinding assembly or arrangement for a rotary cutterhead or chopper arrangement, the grinding assembly including a grinding stone for the grinding of the knives of the cutterhead or chopper arrangement, and a stone positioning apparatus or stone moving arrangement for effecting movement of the grinding stone over the width of the cutterhead, where individual locations of the knives can be associated with differing grinding times.
U.S. Pat. No. 4,843,767 describes a grinding arrangement for a chopper arrangement, in which the grinding stone traverses the width of the chopper drum back and forth with constant velocity. At each of the reversal points at the left and the right end of the chopper drum, the grinding stone remains stopped for a dwell time so that at that location the knives of the chopper drum are ground over an interval of time that is longer than the grinding time that is associated with the parts of the knives located between the reversal points.
During the operation of a forage harvester, the knives fastened to the chopper drum wear over time. While the knives around the circumference of any given location along the width of the chopper drum, as a rule, wear approximately at a uniform rate, the wear across various locations along the width of the chopper drum may vary considerably. Hence the diameter of the enveloping cylinder described by the cutting edges of the knives can vary across the width of the chopper drum. A cylindrical or slightly concave shape of the entire enveloping cylinder is desired in order to simplify an automatic adjustment of the shear bar or to make this possible in the first place, depending on the adjustment system. A parallel and exact in-feed of the shear bar towards the circumference of the chopper drum is indispensable for an effective chopping process.
With known grinding arrangements no possibilities are provided to equalize automatically the deviations from the cylindrical shape of the chopper drum during the grinding process.
According to the present invention, there is provided an improved grinding assembly or arrangement for grinding the knives of the cutterhead or chopper drum of a forage harvester.
An object of the invention is to provide a grinding assembly or arrangement including a stone positioning or moving apparatus having a control for controlling the movement of the grinding stone of the grinding assembly or arrangement relative to a cutterhead in such a way that the amount of time the grinding stone occupies any one location along the width of the cutterhead may be selectively varied.
A more specific object of the invention is to provide an arrangement for controlling the movement of a grinding stone by selecting the path and time characteristic of the movement of the grinding stone as desired so that the grinding stone dwells for a longer time at certain locations along the width of the cutterhead, where the knife edges are worn very little, than at other locations along the width of the cutterhead where the knife edges are worn relatively heavily.
Yet a more specific object of the invention is to provide an arrangement for controlling the movement of a grinding stone by establishing, and storing in memory in advance, grinding times based on empirical values (as result of tests) or values determined by experience, and by storing a desired target shape of the cutting edges of the knives.
These and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings.